Summary/Abstract Tissue-resident memory T cells (TRM) that reside within the non-lymphoid tissues provide superior immunity against a variety of pathogens including influenza virus infection compared to the circulating memory T cells. Currently, the molecular and metabolic mechanisms regulating CD8 TRM programming, maintenance and functions in the tissue are incompletely understood. Unravelling novel mechanisms by which lung protective TRM responses are regulated following influenza infection may aid the design of future influenza therapeutics and/or influenza vaccines. The long-term objective of this grant is to investigate the molecular mechanisms regulating the development of protective CD8 T cell immunity in the respiratory tract during influenza infection. We recently have identified the transcription factor, Bhlhe40, plays a central role in regulating the fitness and function of influenza-specific CD8 TRM. In this application, we hypothesize that non-canonical TGFbR signaling, through TAK1/Gadd45b-dependent pathway, facilitates Bhlhe40 expression and TRM mitochondrial health, thereby promoting the maintenance and protective functions of TRM against influenza infection. Three specific Aims are proposed: Aim 1: To determine the underlying mechanisms by which Bhlhe40 promotes protective TRM responses following influenza infection. Aim 2: To elucidate the roles of non-canonical TGFBR signaling, mediated through TAK1-Gadd45b pathway, in regulating TRM development and/or maintenance. Aim 3: To define the roles of mitochondrial fitness, modulated by TAK1-Gadd45b- Bhlhe40 pathway, in regulating TRM responses and protective function. Each year, influenza virus infects 5?10% of adults and 20?30% of children, killing as many as 500,000 people globally. Understanding the cellular and molecular mechanisms regulating the formation and/or maintenance of lung protective TRM responses following influenza infection and/or immunization may aid the design of future influenza therapeutics and novel influenza vaccines.